REMADE: Update query to ORM for faster paginated responses, fix some bugs

[mpkasp]

Thanks @princess-fixturfab - looks like this should be an easy merge into master.

• Update user in model/admin to reference from AUTH_USER_MODEL
• Update query to ORM for faster paginated response
• Fix 500 error on subpart edit save
• Fix part class is getting ignored in pagination
• Add option to change login for BOM